Atomic frequency standards and high performance crystal oscillators are used in navigation and communication satellite systems. For example, GPS satellites use rubidium (Rb) atomic frequency standards or cesium (Cs) atomic frequency standards to generate signals in space with a very precise frequency for GPS users. Although atomic frequency standards are well known for their frequency precision and stability, atomic frequency standards are also known to exhibit slight, but nonetheless significant, frequency jumps, caused by either environmental and external or internal clock physics perturbations. In the GPS system, an unintended fractional frequency jump could produce a large user range error after just a few seconds. Following a frequency jump, it is consequently desirable to quickly determine the magnitude of the frequency jump, identify the source of the jump, and if needed, apply corrective actions.
Currently, the GPS ground station monitors the health of the GPS satellite by post-processing the satellite signals. Clock frequency corrections and health status are uploaded to the satellites daily. However, for a moderate sized frequency jump, the user range error could build up to an unacceptably high level in less than a day, negatively affecting some precision navigation applications. It is therefore desirable to have an on-board system to autonomously and continuously monitor the performance of the frequency standard and alert the user, or take the satellite out of the navigation solution, if frequency jumps exceed a critical level. Frequency jump detection is a difficult problem, without a viable solution. These and other disadvantages are solved or reduced by using the invention.